The ultimate objective of the proposed study is to further develop a set of measures capable of assessing the integrity of cognitive-behavioral treatments (CBT) for anxiety in youths. Despite the success of CBT for child anxiety in controlled trials, measurement gaps in the field limit efforts to (a) refine and optimize the effectiveness of CBT, and (b) evaluate the success of CBT clinician training efforts. Indeed, there is a paucity of evidence-based measurement strategies to assess the integrity of efforts to implement CBT programs for child anxiety and none that incorporate the three dimensions of integrity. The proposed study addresses this significant methodological gap through the further development and validation of a set of observational measures designed to assess the key components of treatment integrity-treatment adherence, therapist competence, and treatment differentiation-concerning CBT for youths with anxiety. The project will accomplish two primary aims: (a) Establish reliability (interrater reliability, internal consistency, generalizability) and validity (convergent, discriminant) for the treatment integrity measures; and (b) Provide evidence linking data from these measures to (i) child outcomes, and (ii) therapy input variables (e.g., client, therapist characteristics). Recorded therapy sessions from three randomized clinical trials (RCTs; efficacy and 2 effectiveness trials) evaluating CBT for youth with primary anxiety disorders will be used to accomplish these aims. The research project progresses through three phases. In Phase I, the psychometric properties of the treatment integrity measures will be assessed using recorded therapy sessions of CBT for anxiety in youths from one efficacy and one effectiveness trial. The psychometric data provided in Phase I will be used to refine the measures during Phase II. The measures will then be used in Phase III to code archived therapy sessions of CBT for anxiety in youths from an effectiveness study. The resulting data will be used to investigate key questions of theoretical and practical interest, with an eye toward optimizing the effectiveness and efficiency of CBT, including: (a) Exploring the relations among treatment adherence, competence, differentiation, and outcomes in CBT for anxiety in youth; and (b) Identify sources of variation in the integrity of CBT for anxiety in youth. The proposed study is the first to examine the relation between the three integrity components (treatment adherence, competence, differentiation) and clinical outcomes in CBT for children with anxiety disorders. Moreover, the measures produced by the proposed study may be used as a gold standard against which to validate parent- and therapist report measures of integrity.